There are proposed an anode gas non-circulation type fuel cell system and an anode gas circulation type fuel cell system for a fuel cell system. The anode gas non-circulation type fuel cell system does not circulate an anode gas, which is a fuel gas, and discharges an anode off-gas after a reaction together with a cathode off-gas. The anode gas circulation type fuel cell system circulates the anode gas, and additionally supplies the anode gas from a high pressure tank as necessary.
In order to supply the anode gas to a fuel cell (a fuel cell stack), a high pressure anode gas stored in the high pressure tank is depressurized to a medium pressure via a medium pressure control valve, and corresponding to a load request and an operating state of the fuel cell, the medium pressure anode gas is supplied to the fuel cell at a predetermined duty ratio by an anode pressure control valve disposed in a downstream of the medium pressure control valve.
The anode pressure control valve usually uses a normally closed solenoid valve, which is an ON/OFF type valve internally including a solenoid coil. A duty ratio of the anode pressure control valve is operated by a controller that controls the entire fuel cell. A drive signal to the solenoid coil is supplied via a DC/DC converter for a high-voltage battery or a fuel cell. Therefore, while the fuel cell system is operating, a voltage of this drive signal is stable.
With such a solenoid valve, an operating state is susceptible to a temperature change in a usage environment. That is, the temperature change in the usage environment changes, for example, an electrical resistance of the solenoid coil of the solenoid valve and a sliding resistance of a plunger as a movable iron core.
In view of this, even though the drive signal with an identical duty ratio is output to the solenoid valve, a valve opening degree of the anode pressure control valve is possibly different depending on the usage environment. In particular, at a first activation of the fuel cell system, such an influence becomes remarkable since the drive signal is not supplied to the solenoid valve for a while.
When a usage environment temperature is below zero, the fuel cell system is activated below zero. Then, there has been a problem that, at a first driving of the anode pressure control valve, a reaction of the plunger cannot follow the duty ratio to cause an anode gas pressure inside the fuel cell to overshoot.
In order to solve such a problem, for example, JP2998549B discloses a control device for a current control type solenoid valve that directly or indirectly measures an electrical resistance of a solenoid coil of a solenoid valve to change a feedback gain of a controller on the basis of the result.
JP2008-273338A discloses a braking control device that estimates an ambient temperature of the braking control device to estimate a temperature of a solenoid coil (a coil temperature) of a solenoid valve on the basis of a temperature transmission characteristic of the solenoid valve with respect to the estimated ambient temperature to correct an output duty ratio of the solenoid valve in accordance with the estimated coil temperature.